TWR CALLED A GAR WHEN SPACING BECAME TOO TIGHT WITH ACFT TAKING OFF ON THE SAME RWY. AN INCORRECT HEADING FOR THE GAR WAS ISSUED AND REFUSED. SEE AND AVOID RESOLVED THE CONFLICT IN COORDINATION WITH THE LOCAL CTLR.

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THE TWR CTLR INSTRUCTED US TO GAR AT APPROX 300 FT AGL; BECAUSE AN ACR X ACFT WAS VERY SLOW IN HIS TKOF ROLL. A HEADING OF 280 DEGS WAS IMMEDIATELY FLOWN AS INSTRUCTED ON THE GAR. I LOOKED OUT MY L SIDE VIEW WINDOW AND OBSERVED ACR X ACFT CLIMBING DANGEROUSLY CLOSE BENEATH US. THE TWR CTLR; SOUNDING VERY RUSHED; INSTRUCTED US TO MAKE A L TURN TO 180 DEGS. I INSTRUCTED THE FO TO TURN 20 DEGS TO R AND ADVISED TWR CTLR 'NEGATIVE ON L TURN WE ARE TOO CLOSE TO ACR X; WE ARE ON A 300 DEG HEADING; WHAT ALTITUDE DO YOU WANT.' TWR CTLR INSTRUCTED US TO MAINTAIN 4000 FT. THE CLIMB WAS STOPPED AT 4200 FT AND RETURNED TO 4000 FT. IF I HAD COMPLIED WITH THE L TURN INSTRUCTION OF 180 DEGS; I WOULD HAVE FLOWN DIRECTLY OVER ACR X CLIMBING ACFT WHOM WAS ALREADY TOO CLOSE AND STILL GETTING CLOSER. ESTIMATE VERTICAL SEPARATION WAS 500 TO 700 FT. HORIZONTAL SEPARATION WAS 0 TO 80 FT. (ACR X R WING APPEAR TO BE UNDER OUR L WING.) IN ADDITION; RWY 27L WAS ALSO IN OP; WE HAD BEEN APCHING FOR RWY 27R. RWY 27'S PARALLEL ARE VERY SELDOM USED IN DTW. I BELIEVE CONTRIBUTING FACTOR MAYBE LACK OF EXPERIENCE OF TWR CTLR IN A GAR SIT OF SELDOM USED RWY 27 PARALLEL APCHS. THERE WAS AN ACFT ON TXWY DELTA TAXIING ONTO RWY FOR DEP AND WE WERE CLRED TO LAND. THE ACFT EVENTS WERE TOO CLOSE BEFORE OUR INSTRUCTED GAR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: CALLBACK REVEALED THAT THE RWY CONFIGURATION WAS NOT THE NORMAL ONE. THE LOCAL CTLR APPEARED TO BE CTLING BOTH RWYS. ONCE THE CONFLICT BECAME APPARENT AND THE RPTR ADVISED OF THE REFUSAL OF THE ASSIGNED HEADING; ANOTHER CTLR STEPPED IN TO RESOLVE THE CONFLICT.